British researchers looked at data from about 165,000 people, and found that a 10 percent rise in body-mass index (BMI) was linked with a 4 percent drop in concentrations of vitamin D in the body. BMI is a measurement of body fat based on height and weight.

The link between BMI and vitamin D levels was found in men and women, as well as in younger and older people, the investigators noted.

The findings suggest that a higher BMI leads to lower levels of vitamin D circulating in the body, while a lack of vitamin D has only a small effect on BMI, according to the authors of the study, published Feb. 5 in the journal PLoS Medicine.

Efforts to tackle obesity may also help reduce levels of vitamin D deficiency, said lead investigator Dr. Elina Hypponen, of University College London's Institute of Child Health.

Previous studies have linked vitamin D deficiency with obesity, but it wasn't clear whether a lack of vitamin D triggered weight gain or whether obesity led to vitamin D deficiency, the study authors noted in a university news release.

Vitamin D, which is essential for healthy bones and other functions, is produced by the skin when exposed to sunlight. It can also be obtained through foods and supplements.

"Vitamin D deficiency is an active health concern around the world. While many health messages have focused on a lack of sun exposure or excessive use of suncreams, we should not forget that vitamin D deficiency is also caused by obesity," Hypponen said.

"Our study highlights the importance of monitoring and treating vitamin D deficiency in people who are overweight or obese, in order to alleviate adverse health effects caused by a lack of vitamin D," she added.

Although the study reported that higher BMI leads to lower levels of vitamin D circulating in the body, it did not prove a cause-and-effect relationship.

More information

The U.S. National Institutes of Health, Office of Dietary Supplements, has more about vitamin D.